As users are increasingly relying upon portable computing devices, and are utilizing these devices in an increasing variety of scenarios for an increasing variety of purposes, it can be desirable to further improve the quality and capabilities of these devices. For example, these devices are often dropped or subject to potential stresses, such that it can be desirable to further improve the durability of these devices. It also can be desirable to allow various components to be more easily replaced or upgraded in order to further extend the lifetime of these devices. It also can be desirable to continue to improve the capabilities and accuracy of these devices.